XkbVarient breaks NixOS Rebuild

I am trying to change my default configuration to Colemak using the code shown below in my etc/nixos/configuration.nix.

console.useXkbConfig = true;
services.xserver = {
  layout = "us";
  xkbVariant = "colemak_dh_iso";
  xkbOptions = "caps:swapescape";
};

When I try to run nixos-rebuild switch, I recieve the following error message.

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